1. Field of the Invention
This invention relates to a rolling diaphragm sealing device between the wall of a housing bore and an internal part, with one of the part and the housing being reciprocable relative to the other.
2. Description of the Prior Art
It is known to provide a rolling diaphragm sealing device between the wall of a housing bore and an internal part which reciprocates relatively to the wall. The sealing device comprises two rolling diaphragms whereof the annular mouths open towards each other and whereof the internal annular edges are secured to the internal part and the external annular edges to the housing in a fluid-tight manner, each rolling diaphragm bounding an annular chamber filled with a supporting liquid and closed by an annular seal. Each seal has a sealing effect in only one direction of reciprocation and is associated with a sealing surface which slides thereon when the internal part reciprocates. A rolling diaphragm sealing device of this kind is shown and described in German Patent Specification No. 1,080,366, for example.
If a rolling diaphragm sealing device of this kind were to be subjected to pressure unilaterally, more particularly high pressure, the liquid would be displaced from the loaded chamber by way of unavoidable leaks in the associated annular seal into the non-loaded chamber, which would have the result that the rolling diaphragm remote from the pressure would be over-expanded and finally destroyed, that is to say the known rolling diaphragm sealing device is not suitable for unilateral high pressure loading.